Electrical impulse timing instrument



Sept. 18, 1956 wA F. BLooM ELECTRICAL IMPULSE TIMING INSTRUMENT FiledOct. 16, 1952 United States Patent O ELECTRICAL IMPULSE TIMINGINSTRUMENT William F. Bloom, Dayton, Ohio Application October 16, 1952,Serial No. 315,130

14 Claims. (Cl. 307-132) This invention relates to instruments forcontrolling the opening and closing of an external electrical circuit.Although not so limited, the invention has especial application to thetesting of electrical devices such as relays.

The constant trend toward attaining higher speed operation of protectiverelays and auxiliary equipment has been apparent in the field of powertransmission and distribution for many years. lt has been the experienceof those in the field that the testing of such relays and equip ment bythe application of current or potential does not always constitute acomprehensive test of the apparatus being inspected. In many instances,the fitness of a relay for service can be truly determined only by theapplication of energy for a short, definitely measured interval of time.The instant invention is aimed generally at the provision of aninstrument designed to produce and accurately to measure electricalimpulses for this and like purposes.

Another object of the invention is to produce a device which willcontrol an external circuit in a manner best suited to the relay orpiece of electrical equipment being tested or operated. A pre-determinedtime interval is established, for example one cycle of a 60 cyclecurrent supply. In some instances it is desirable to close the externalcircuit once during each cycle. For other purposes it is desirable thatthe closed circuit be established at a frequency less than one cycle. lnstill other instances it is desirable that the device act a single timeupon the external circuit and then continue to operate at synchronousspeed but without producing a control operation until manually reset bythe operator. Each of these three modes of operation can be selected andproduced at will by the device being described. Further, the frequencyof the control operation can be preselected, and, sitll further, theexternal circuit may be opened instead of closed in any of the threemodes of peration described, all of these operations and the resultsproduced thereby being a part of the object of this invention.

A further object of the invention is to incorporate impulse controlapparatus as described in an instrument which is sturdy and reliable ofadjustment, and which is small enough to be considered portable forpurposes of field Work. That is, the instrument is not confined tolaboratory work but can be carried into the eld and applied directly tothe test problem at hand.

Still another object of the invention is to vary the duration of appliedelectrical impulses through a relatively wide range of fractionalincrements of a predetermined time interval, for example one second.

Other objects and structurual details of the invention will appear fromthe following description when read in connection with the accompanyingdrawings, wherein:

Fig. l is a diagrammatic view of the instrument in its illustrativeembodiment, and

Pig. 2 shows a structural detail of such instrument.

Referring to the drawings, the instrument which may be suitablyconstructed in portable form presents a pair of terminals 11 and 12 forattachment of the instrument in an external electrical circuit. Such acircuit is indicated at 13 and interposed in the external circuit is adevice 14 to be tested. lt will be understood that, in accordance withthe purpose of the instrument, the establishing of an electricalconnection between the terminals 11 and 12 results in the closing of thecircuit 13 through the device 14 for such a time interval as theelectrical connection between the terminals 11 and 12 is maintained.

The electrical interconnection between the terminals 11 and 12 isestablished by an internal circuit including leads 15 and 16 connecteddirectly to the respective terminals 11 and 12. At the ends opposite theterminals 11 and 12, the leads 15 and 16 terminate in contacts 17 and18. Such contacts are part of a switch unit 19 which further includes apair of opposed contacts 21 and 22 and central contacts 23 and 24permanently connected to the switch element. The switch unit 19, it willbe observed, is of the two pole, double throw kind. Thus, it isadjustable selectively to connect the contacts 23 and 24 to the contacts17 and 18 or to the opposing set of contacts 21 and 22.

The central, common, contacts 23 and 24 of the switch 19 represent theterminals of respective leads 25 and 26. The lead 25 is directlyconnected to a stationary elecv trical brush contact 27 forming a partof a rotary timing switch device 28. The lead 26 is indirectlyconnected, by way of a selector switch device 29 and a stepping switchdevice 31, to an adjustable or movable electrical brush contact 32 alsoforming a part of the rotary switch 28.

The rotary switch device 28 further comprises a disc 33 of insulatingmaterial mounted on a shaft 34 to rotate in a clockwise direction at aconstant speed, for example, one revolution per second. Power forrotating the disc 33 is supplied by a synchronous motor 35 actingthrough suitable speed reducing gearing (not shown). As indicated, themotor 35 is connected to a source of 120 volt, 60 cycle alternatingcurrent, the supply of which is controlled by a manually operated switch36. A segment 37 of conducting material is rigidly attached to theperiphery of the disc 33. This segment extends along the circumferenceof the disc in an arc of slightly less than The electrical brush contact27 is in such overlying, adjacent relation to the periphery of the disc33 as to be engaged by the segment 37. The movable electrical brushcontact 32 is similarly mounted and is adjustable in its relation to thexed contact 27 so as to occupy a position nearer to or more distant fromthe iixed contact in an arcuate or circumferential sense. The movablebrush contact may be adjusted forward or backward through a pathextending from a point directly over the fixed contact 27 to a pointdiametrically opposite the fixed contact.

It will thus be seen, that, when the disc 33 and its attached segment 37are rotated, an electrical circuit will be closed between the contacts27 and 32 for so long as both brushes are in contact with the segment.The duration of this interval of contact depends on both the relativeposi# tion of the brushes and the speed of rotation of the disc, andsince the speed of rotation of the disc is held con-l stant, theduration of such interval of contact will depend entirely on therelative position of the brushes 27 and 32 as determined by the positionof the movable one thereof. The segment 37 extends for an arc ofslightly less than 180 because of the finite thickness of the brushesand in order to prevent a circuit from being established twice duringone revolution of the disc when the brushes are in positiondiametrically opposite one another. The principle of operation of therotating switch is not affected by the rate at which it is rotated, nor,of course, by the. direction of rotation. A speed of one revolution persec- Assuming `the switch unit 19 to be set to engage the contacts 17and 18 then a :circuit is closed through the 'terminals Hand Y12 by Wayof the electrical'brush con# ta'ctsZi vand 32. The vapparatus tends,ithereforeyelectjrically lto 'connect'the terminals V1.l"`ar`1d il.oucedu'ring'ea'ch revolution of the disc' 33 land for a period oftimedeterniirled 'by the relative position of 4vthe 'ibrush'oontacts A27and 32. The :rotary switch device 28 thus tends intermittently to openVand close the'dexternal circuit i3, the frequencyof the *electricalimpulses being 'e function of the lselector switch 29 and 'steppingVswitch 31, as will hereinaiterbe seen. I

"The set of4 contacts 21 "and 2.2, of the switch unit i9, 'is iin-a lead338 extending 'across 4and'intercc-n'nec'tin'g polsiti've and'negativeconductors '39' `and 41 `of adireot'cnrrent sppl'y suitably/'provided'in the instrument, as V'by a v'srhlall rectifier'operating from the C.supply used to drivethelrlotor"35. lAlso' i-n `the lead 38 is a relay 42attracting an armature assembly Aincluding la pfair of movable-contactarms 43 and V44. The Contact arms '43 andiii l"are electrical-lyinterconnectedby a conductor `45. Each, moreover, makes alternatecontact otr engagement with fa'pair 'of-contacts 46 and 47. These inturn are connected to a two pole double throw reversing switch 48'permanently 'connected across the-leadsd and d6. flhefcont'act alms y43and 44 'are nor'mlally urged by a spring@ to a position of engagementwith respective contact farms f3-and 44 "to alterna-te positions ofadjustinent.- These cont-act arms and associated parts re'p-r'esent arlalternate means of Vclosing ythe external circuit-13 and is providedbecause of its ability toh'a'ndle'la heavier cnlrent thanV coul'dbehandled v'by the contacts of `the lrotating switch and also to providefor ca reverse mode of'operation. is, instead 'of havingthe 'eiterrialcircnit I3 normally 'opened 2and 'intermittently closed, it-fiuray 'benormally closed and inte'rr'nittentl'y opened, either imode of operationbeing-selectedbyffadjstmentof thefrevers'ing' switch 4S. rThus,with'thesivitch A4S'set inl e posi-tion illustrated, 'the 'circuitacross i'leads "i5 and 'l5 is vrl'o'rlnally open fand-is closed onlywhen the contact arrris 43 Aand 44 move to 'their alternate position lofadjustment in response to the Venergizing of relay/2. Set toSits'other'position fof adjustment,- howeverptfhe switch 48V-causes the'circuit-across 'leads 'iE-andi' to benoi'- mally -clo'se'd and suchscirouit is intermittently opened by the movement of the arms 43 and 44.

*It will still 'further be vunderstood 'that when the eX-ternalfcircui-t' E73 is under the 'control' of the relay 14,2, inthefsupplementa'l interina-l circuit, the timing 'of theimptxlsesremains a function of the rot-ating swi-tehsi'nce such switchisincl'nded iin tihesupplernental `lc virtue :its attachment Lto 4theVcontacts Z3 an switcli9. Thus, the Vrel'ayf42 @is energized yanddeenergiz'e'd for "greater vor fle's'ser periods during each'revolutiony 'of 4the Ai-rls'trlated dise 33 with 'the result that inlconjunction with'sp I armsr il'lani 44`alef'naoved toalternate-positions of ad 'sement `'du-ring each revo-lution vrof thedisc v3? Vor l ach 'cycle ofoperation as such periodsmay "be termed. p

. Theaprevi'ously referred lto'sele'dtor switch29andstepsta/itchafr'eu'sed to Aselect the frate orefpetition with the'fc'tevicesv abovedescribed v/illact'on the 'est nal'fmciiit is.' YThe "selectorswitchaetdallyeonsists of live units A, B, C, D and E operated on a coni-Y'mon shaft, each unit consisting of a `contact varrrl 51 land fourcontact points 1, 2, 3 and 4. The stepping switch comprises a rotaryseries of contacts 52 and an arm 53 which traverses the series ofcontacts 52 by moving successively from one to another in a clockwisedirection las viewed in the drawing. There are twenty five contacts 52in the illustrated instance. The arm 53 is attached Yto `a rotatableshaft S4, common lalso toa second stepping 'switch 55 'made up 'of "aseries of contacts 56 and an arm 57.

The arms 53 and 57 of the stepping switches 31 and 55 lare moved linlindex fashion by'ian intermittent rotation of the shaft 54.under thecontrol of fand in response to operation of the rotating switch 23.Thus, lapiece of material Sii on the face of the disc 33 operates in acarnlilie fashion momentarily to close a pair of contacts 59 in a lead6i extending across the conductors 39 and 41. Also in the lead 6i ls larelay 62 'which in conjunction with a spring 53 elfect's to 'and 'fromotion of la paw164 in cooperative engagement with a'ratchet 65 ontheshaft 54. It'will be apparent 'that 'a'circuit 'is closed "throughthe relay 62 once 'during 'each 4'cycle 'of movement er the switch2`8. lThus, the jsh'aft 54 is turned 'one step 'in -fa clockwise 'direction'durinff each 'cycle 'of `operati@ 4of the switch Zitand the arms '53and 57 are moved in response thereto 'to engagement 'with the 'nextsucceeding Contact SjZfor 56.

AThe selector switch units D and lEfare interconnected with one-:anotherand with selected points or positions of the stepping' switch 3l. TheseVcn'o'n'uec'tions 'are'selfevident from the drawings.' Generally,however, it''may be seen that position l of the 'selector switch unit -Dis con nested 'to''position orthe first` contact of `switch 341, and isconnected also Vto position 4'4 off the :switch unit D 'and to theswitch 5E. of the switch unit E. 'Position JZO switch unit D isconnected to positions 6, '11, :i6 2.1 'of the/switch 3d 'as lwell YVasto positions 2 'and 4 of unit Position '-3 of selector uriit D lisconnected tot'heam 53 of the switch 31 as well as tothe lead 25extending from the control switch19. 'Position 4 of selector 'ii-nit Dlis connected only asfbeore described. The farm' :5i ofselector unit Dis :connected by lead66 `with the rho* able electrical brush Contact 32.or theswitch device 2S.

With "the -above described parts in Athe position `illustrtated, Yarcircuit Vmay be' traced jfrom one side "of the Vswitch i9 l'by way 'ofthey lead 225 to the rsta'ti'onary i brush contaetf, segment 3i-an-'dvb'rush y32 of the rotating switch@ 'the am sa of switch unit D and fromthere tnr'oughcsntact r1-'timber i of the stepping switshal through thearm l5.3 thereof to the leadfi and A'back "to the -`oppoysite 'side o'fthe 'swltchaa lf it fis assumed that the dise as rotating, their it isobvious tllat-ithee'ircnil thus-traced will be brekenan instant 4laterbi/the 'sep-` arada-n 'of segment 37 and electricalY brush Aczmta'clfNext in order is the operation of the set of contacts@ which the `arm153 of Y'the relay- '31 vtenevanef-y to Contact potuta of fheseries ofcontactsSZ. New, when the rotating .witchA llas-'completed a revelation'nie brush cont cts 2.7 and 32 Awill 'again be bridged by thes'eg'mem37. LAn-'fat'teinpt to Vretrace the circuit as described above will'indicate an 'open enculee-t point 'l1-ofthe stepping switch because the'fis new at Test on point After twenty livev revolutions eff 'therotating-switch fthe 'of the `stepping relay will againbe at vrestonpdsition l fand a complete circuit may be traced las above described.If la silnilaranal'ysis 'of the-cncdit triade with theV selector 'arm -5of Sthe'unit D Ion'posrtlon 2 and 3 lit will be seen that-a'co-mpete:circuit-may beit'na'ced between the opposite side of the controlFs'witch'91during `everyir'th .revolution and every revolution -ofthedisc 33, respectively. Position 4 of theselector-sWitch-is*used in amodified manner of operation `described' below.

'Ihus, Y position 4 of. Vthe selector/unit risutili-zed to initiate aone time or single'action energizing.orlle-A energizing of the externalelectrical circuit. Referring to the selector unit A, the arm 51 thereofis connected by a lead 67 to the positive conductor 39 of thesupplemental internal circuit. Position 4 of the unit A is connectedindirectly in the following manner to the opposite side of thesupplemental circuit or to conductor 41. There extends from position 4of unit A a lead 68 in which is interposed a relay 69 and a reset switch71 and which terminates at a point 72. From the point 72 parallel leads73 and 74 extend. The former is connected to the conductor 41 by way ofa normally open switch 75. The latter is connected to the conductor 41by way of contact points 2, 7, 12, 17 and 22 of the stepping switch 55and the arm 57 thereof, the latter being directly connected through alead 76 with conductor 41. With the arm 51 of the selector switch in itsNo. 4 position a circuit will be closed through the relay 69 when thearm 57 of the stepping switch 55 reaches the iirst of the identiedpositions, Nos. 2, 7, 12, 17 and 22. The energizing of relay 69 effectsmotion of an armature assembly of which the switch 75 is a part. Thenormally open switch 75 thus is closed in response to energizing of therelay 69. This switch now bridges the portion of the relay circuit whichpasses through the stepping switch 55 and so prevents the relay 69 frombeing deenergized when the arm of the stepping switch moves to the nextcontact. That is, the relay circuit is locked in a closed position andthe stepping switch 55 is rendered ineffective to open or close suchcircuit. Also forming a part of the armature assembly inliuenced by therelay 69 is a switch 77 interposed in the lead 26 extending from oneside of control switch 19. The switch 77 is normally closed but inresponse to energizing of the relay 69 moves to an open position. As aresult, the circuit through the control switch 19 is opened and thetiming apparatus is rendered ineffective with respect to the terminals11 and 12 and the external circuit 13 attached thereto.

The relay circuit is manually opened or reset by operation of the resetpush button 71. After the relay circuit is reset, the switch 77 willclose and the switch 7S will open. This condition of the parts willprevail until the arm of the stepping switch 31 reaches a point 1, 6,11, 16 or 21, depending on the position in the indexing sequence atwhich the relay 69 is reset. When the arm of the stepping switch reachesthe first one of these positions one control operation of the apparatusresults. Immediately following this control operation, and as a part ofthe same revolution of the switch 28, the stepping switch advances tothe next indexing position, wherein the arm 57 of switch 55 will engagea position 7, 12, 17 or 22. Accordingly, the circuit is again closedthrough the relay 69 and the switch 75 is closed and the switch 77 isopened with the result as before described.

It is desirable that the relay 69 be not reset at such time as the armof stepping switch 31 is on any one of the positions 1, 6, 11, 16 or 21,in which position a control operation would result. So that the operatormay know at what times the stepping switch reaches these positions, oneof two lamps is caused to light. With the relay 69 energized anindicating circuit is connected to a red lamp 78 through a switch 79.When the relay 69 is open or rest the indicating circuit is transferredto a white lamp S1 by the opening of the switch 79 and the closing ofanother switch 82, the switches 79 and 82 being a further part of thearmature assembly shown in Fig. 2 as operating under the inuence of therelay 69.

The red lamp 78 and the white lamp 81 are thus alternately usedaccording to whether the relay 69 is energized or deenergized. Inoperation of the apparatus when the relay 69 is deenergized the whitelamp 81 will light when the stepping switch reaches its first controlproducing position, and upon each succeeding control pro ducingposition. When the selector arm 51 is adjusted to its No. 4 controlposition and the relay 69 is brought into the circuit, the red lamp 78will be used.

The sections or units B and C of the selector switchv device 29 are usedto control the signal lamps 78 and 81. The arm 51 thereof has a commonconnection to the lamp by way of the switches 79 and 82. These units,moreover, are wired or connected to the contact 56 of the steppingswitch 5S in the same manner that corresponding positions of the units Dand E are connected to the contact 52 of the stepping switch 31. Thiscauses the selected lamps to light during the cycle of operation of therotating switch 28 in which a control operation is produced. In the caseof the red lamp circuit, therefore, the lighting of the red lamp giveswarning that the next operation of the instrument is to be a controloperation and means that the operator should not at that moment push thereset button 71.

What is claimed is:

l. An instrument for controlling the opening and closing of an externalelectrical circuit, including a pair or terminals, a rst switchingdevice for intermittently opening and closing a circuit between saidterminals, said device including cyclic means moving through successiveoperational cycles, a second switching device for intermittently openingand closing a circuit between said terminals, said second deviceincluding an intermittently energized and deenergized relay, a controlswitch setable to alternate positions of adjustment selectively to connect said terminals, said switch acting in one position to connect saidcyclic means directly to said terminals and acting in another positionto place said cyclic means in series relation to said relay.

2. An instrument for controlling the opening and closing of an externalelectrical circuit, including a pair of terminals, respective conductorsextending from said terminals, other conductors representingcontinuations of the first said conductors, a switch element connectedto said other conductors and adjustable to alternate posi tions ofadjustment, in one of which it is engaged with the first saidconductors, a rotary switch device connected to said other conductorsand operable intermittently to close a circuit between said otherconductors, and another switch device effective in response toadjustment of said switch element to the other of its alternatepositions of adjustment to close a circuit through the first saidconductors, said other switch device effecting intermittent closing ofsaid last named circuit in response to operation of said rotary switchdevice.

3. An instrument for controlling the opening and closing of an externalelectrical circuit, including a pair of terminals for attachment of theexternal circuit to the instrument, a pair of conductors in saidinstrument representing a supplemental, continuously energizedelectrical potential, a relay interposed between said conductors andenergized thereby, a switching device settable by the energizing anddeenergizing of said relay to alternate positions of adjustmentelectrically interconnecting and disconnecting said terminals, a switchelement in series relation to said relay and operable when closed toenergize said relay, and another switching device brought into seriesrelation with said relay in the closed position of said switch elementeffecting intermittent closing and opening of the circuit through saidrelay.

4. An instrument according to claim 3, characterized in that said otherswitching device includes a rotary element turning at a constant speed,an electrically conductive segment on said rotary element, and brushcontacts electrically bridged by said segment during the interval ofturning motion of said rotary element in which both said brush contactsengage said segment.

5. An instrument for controlling the opening and closing of an externalelectrical circuit, including a pair of terminals for attachment of saidinstrument in the external circuit, a switching device settable toalternate positions of adjustment to close and open the circuit throughsaid terminals, a supplemental electrical circuit in said instrumentincluding a relay eiecting alternating adjustment of vsaid switchfdevice-in responseto energizing and deenergizing thereoffarotating switchdevice including an intermittently bridge pair of contacts, 'andacontrol switch settable to 'a rstxposition closing said Vpair ofcontacts in series with said terminals and settable to a second positionclosing said contacts in serieswith said relay, said Acontrolswitchjopening the supplemental circuit lthrough said relay in movingfrom said second to said first position.

6. An instrument according toclairn 5, characterized by a manuallyadjustable `reversing switch between the rst said switching device andsaid terminals.

7. An instrumentV for controlling the .opening and closing of an`external electrical circuit, including -a fpair of terminals forattachment of -said .instrument Yin said circuit, an internal circuitbetween said terminals Vincluding in series arrangement anintermittently lopened and closed switch and another switch adjustableto positions opening and closing said-internal'circuit and normallyoccupying one of said positions, asupplemental inernal circuit includinga relay, said other switch being movable by energizing of said relay tothe other one of its said positions, a stepping switch operating insynchronism with said intermittently operating switch, certain positionsof said stepping switch lbeing connected in series with said relaywhereby to close said supplemental circuit through said relay in saidcertain positions of said stepping switch, a Vholding circuit energizedin response to the energizing of's'aidrelay to hold the circuit throughsaid relay closed irrespective ofthe position of said stepping switch,and a manually operable switch in said supplemental circuit toy renderthe described devices in said supplemental circuit alternativelyeffective and ineffective.

8. An instrument according to clai t 7, characterized by a signal lightin said supplemental circuit in-series relationto positions'of saidstepping switch in respectively preceding relation to saidcertainpositions, and va vswitch operated Vby and in yconjunction withsaid manually operable switch .for closing and opening said supplementalcircuit through said lsignal light.

9. An instrument according to claim 7, ycharacterized by manuallyoperable reset meansifor opening said holding circuit irrespectiveofthe-position of said 'manually operable switch.

l0. An instrument VYfor controlling thev opening rand closing of anexternal electrical circuit, including a pair of terminals forattachment of said instrument in .said circuit, an internal circuitinterconnecting said terminals and including a rotary switch turning ata constant-speed intermittently opening and closing said internalcircuit, another switch in said internalV circuit adjustable topositions opening and closing said internal circuit and normallyoccupying one of said positions, a 'supplemental internal circuitincluding a stepping switch adjusting to successive index positions incorrespondence with motion of said rotating switch through successiveupredetermined degrees of rotary movement, certain of said indexpositions being connected in said supplemental circuit, relay 'means insaid supplemental circuit operable when energized to move said otherswitch to the other oneiof its said positions, a selector switchadiustable to close the supplemental circuit through -said relay Ymeansin thefsaid certain positions of .said selector switch, and a holdingcircuit including a switch element-connected toV and movable with saidctherswitch for holding said relay means energized through .positions ofadjustment of said stepping switch successive to the first Vencounteredone ofv said certain positions, andvvmanually operablereset means Vforopening-said `holding circuit.

V.1-1. ,An instrumentV according to claim' l0, character ized by anotherstepping switch in series vrelation tosaid rotating switch in the firstsaidinternal circuit and adjusting in synchronism with the first saidstepping switch, index positions of said other stepping switch beingconnected in said internal circuit which occupy respectively precedingrelation to the corresponding said certain positions of the first saidstepping switch.

l2. An instrument for controlling the opening and closing of an externalelectrical circuit, including ajpair of terminals, a cylindrical member,means for rotating said member at a constant speed, an electricallyconductive segment fastened to said cylindrical member fand extendingover-a portion of the circumference thereof, a pair-of electrical brushcontacts in the path of movement of said conductive segment, saidcontacts being connected to respective terminals so that a circuit isclosed through said contacts during that part of each revolution of saidcylindrical member in which both said contacts are in engagement withsaid segment, an adjustable mounting for one of said contacts whereby itmay be moved closer to or more distant from the other one of saidcontacts correspondingly to increase and to reduce the time interval inwhich the circuit is closed through said contacts, and selective switchmeans in seriesrelation to one of said electrical brush contactsselecting certain-only of the revolutions of said cylindrical member inwhich-the circuit is closed through said contacts.

A13. An instrument for controlling the opening tand closing of anexternal electrical circuit, including avpair of terminals, a steppingswitch having a common contact connected to one of said terminals and aseries of Vcontacts connected successively to said common contact by anindexing oper-ationof said stepping switch, means for effectingsuccessive indexing operations of said stepping switch, a selectorswitch including Va plurality Vof relatively stationary contactsconnected to respective contacts or groups of contacts in the series ofcontacts of said stepping switch, and further including a movablecontact selectively engageable with said stationary contacts Tandconnected to the other one of said terminals, means forsupplying-intermittent electrical impulses -to said movable contact, anda rotating switch interposed between said selector Vswitch and Vsaidother terminal, including a Vpair of relatively adjustable switchcontacts and electrically conductivemeans for closing a circuit throughsaidtpairY of contacts during a .portion of each rotary movementlofVsaid rotating switch.

14. lElectrical pulse, generating means,.including a icylindrical.partrotating at a constant speed, an electrically conductivesegmentextending approximately one-half'the distance .about the, peripheryofsaidflpart and .rotating therewith, brush contacts arranged tobevbridged bys'aid segment during a part of'each revolution of saidpart, a. circuit closed by the bridging of said contacts, means forvanyingthe duration of the pulse transmitted by said circuit withina'range covering fractions of the time required for said part tocompleteone-half revolution,` and selector switch means in said'circuitproviding for closing of said circuit upon preselectedcertain ones onlyof the revolutions of said part.

:References Cited in the le of this `patent UNITED STATES PATENTS

